Development of pancreatic lipase in coldwater marine fish larvae

Little is known about lipolytic activity and digestion in fish. Based on a few studies with adult fish the most important digestive lipase in fish to be a pancreatic, bile salt-dependent lipase. In the prese nt study this lipase has been quantified and localised in cod (Gadus morhua) larvae from hatching to day 31 after hatching. The larvae wer e kept at 12°C and start-fed with microalgae (Isochrysis galbana and Tetraselmis sp.) from day 4, enriched rotifers from day 5 and enriche d Artemia from day 17. An ELISA assay was developed to quantify the a mount of lipase in the larvae by use of an antiserum against cod lipa se. The same antiserum was utilised to localise the lipase by immunoh istochemistry on cryosections of larvae. The development of lipase in cod larvae can be divided into at least 3 phases, which were correla ted to the age of the larvae The first phase is directly after hatchi ng (day 0) until day 2, when the lipase levels were rather low, altho ugh detectable. In the later yolk sac phase the content increased sli ghtly, as the larvae started to synthesize lipase. From first-feeding (day 5) onwards, an exponential increase in lipase levels was appare nt. The lipase content was positively correlated to the dry weight of the larvae, but did not seem to be influenced by the lipid content o f the feed. The lipase was localised in the pancreas and in the micr ovilli layer before exogenous feed uptake (day 3). At later stages, p resence of lipase was also observed in some vacuoles in the gut epith elial cells, but not in other tissues or in food organisms.The lipase antiserum cross-reacted with turbot lipase and comparative first-fee ding experiments with turbot (Scophthalmus maximus) using different d ensities of live feed organisms in the larval tanks were carried out.